The primary contacts made between cells and the surrounding environment, including contacts with other cells, are mediated by the transmembrane proteins known as integrins. These contacts are critical for the bidirectional transduction of signals to the interior of the cell and consequently to the modulation of biochemical pathways. Integrins are heterodimeric cation-dependent membrane-spanning glycoproteins that mediate cell adhesion, migration and signal transduction. Integrins are composed of an alpha and beta subunit and to date, 8 beta and 15 alpha subunits have been identified which combine to form over 20 different .alpha..beta. heterodimers. Integrins have been found in all tissues examined and consist of a large extracellular domain, a transmembrane domain and a smaller cytoplasmic domain. It is the extracellular domain of the integrin that acts as a receptor for various matrix proteins, while the cytoplasmic domain has been shown to interact with actin filaments of the cytoskeleton and with cytoplasmic proteins such as talin, paxillin, filamin and focal adhesion kinase (FAK) (LaFlamme et al., Matrix Biol., 1997, 16, 153-163). Recently, four additional proteins that interact with .beta.-integrin subunit cytoplasmic domains were reported. Of the four, only the ankyrin repeat containing serine/threonine protein integrin-linked kinase (ILK) has been shown to bind multiple forms of the integrin beta subunit (Dedhar and Hannigan, Curr. Opin. Cell. Biol., 1996, 8, 657-669; Hannigan et al., Nature, 1996, 379, 91-96).
Integrin-linked kinase (also known as ILK and p59ILK) was originally identified from a two-hybrid screen of a human placental cDNA library by its ability to bind to and phosphorylate the .beta.1-integrin cytoplasmic domain (Hannigan et al., Nature, 1996, 379, 91-96). Characterization of integrin-linked kinase in these studies also revealed that overexpression leads to disrupted epithelial morphology of IEC-18 cells, decreased cell adhesion to extracellular matrix substrates as well as anchorage-independent growth (Hannigan et al., Nature, 1996, 379, 91-96). Others have shown that overexpression of integrin-linked kinase leads to stimulation of the cell cycle, fibronectin matrix assembly, reduced expression of E-cadherin and malignant transformation (Radeva et al., J. Biol. Chem., 1997, 272, 13937-13944; Wu et al., J. Biol. Chem., 1998, 273, 528-536). Interestingly, the integrin-linked kinase gene, which maps to chromosome 11p15.5, is located in a region associated with genomic imprinting, whereby the expression level of the alleles of a gene depends upon their parental origin and loss of heterozygosity in certain tumor types (Hannigan et al., Genomics, 1997, 42, 177-179).
The expression pattern of integrin-linked kinase is distributed among most human tissues and has been shown to be overexpressed in certain tumors, those being Ewing's sarcoma, primitive neuroectodermal tumor (PNET), medulloblastoma and neuroblastoma (Chung et al., Virchows Arch., 1998, 433, 113-117). Recently it was demonstrated that integrin-linked kinase expression is regulated by erbB-2, a member of the epidermal growth factor receptor family, which plays a pivotal role in epidermal growth and differentiation. The investigators showed that overexpression of erbB-2 led to a specific increase in integrin-linked kinase expression in several regions of epidermal tissue (Xie et al., Am. J. Pathol., 1998, 153, 367-372). These studies implicate integrin-linked kinase in skin development and the pathogenesis of skin diseases.
Integrin-linked kinase also triggers the LEF-1/beta catenin signaling pathway when overexpressed, indicating a role in the activation of transcription within the Wnt signaling cascade (Novak et al., Proc. Natl. Acad. Sci. U.S.A., 1998, 95, 4374-4379). The activity of integrin-linked kinase has been shown to be modulated within other signaling pathways including those involving G-proteins (Tu et al., Mol. Cell. Biol., 1999, 19, 2425-2434) phosphotidylinositol 3-kinase, protein kinase B and glycogen synthase kinase 3 (Delcommenne et al., Proc. Natl. Acad. Sci. U.S.A., 1998, 95, 11211-11216). These results indicate that integrin-linked kinase may play a role in insulin-dependent responses in the cell and possible in the development of diabetes.
Currently, there are no known therapeutic agents which effectively inhibit the synthesis of integrin-linked kinase. Consequently, there remains a long felt need for agents capable of effectively inhibiting integrin-linked kinase function.
Antisense technology is emerging as an effective means for reducing the expression of specific gene products and may therefore prove to be uniquely useful in a number of therapeutic, diagnostic, and research applications for the modulation of integrin-linked kinase expression. The present invention provides compositions and methods for modulating integrin-linked kinase expression using antisense technology.